The present invention relates to improvements in free-standing stoves and the like, and in particular to an integral forced air heat exchanger system for such a stove.
Coal and wood burning stoves have long been used for heating buildings, because enclosed stoves are more efficient, generally, than open fireplaces, and because wood usable as fuel is readily available in most localities. While wood remains a comparatively low-cost fuel, with the passage of time the cost of using wood as fuel has greatly increased, and, therefore, efforts have been made to increase the efficiency with which the fuel energy is used. Significant energy saving may be accomplished in the use of these stoves by the addition of a forced air heat exchanger to extract additional heat from the fire, transferring the heat thus extracted to air, and circulating the heated air through the rooms being heated. In addition to utilizing a greater portion of the energy released in the stove, circulation of heated air throughout a room provides a more even distribution of heat within the room whereby remote portions of the heated room may be kept warm without the necessity of over-heating portions of the room closest to the heating stove.
With recent very significant increases in the price of heating oil and gas, the use of wood burning stoves for heating dwellings has increased. This has brought a proliferation of new stove designs, and an increase in the importance of general outward appearance of stoves as a factor determining their marketability. While it would be possible to modify a previously designed stove which heats by radiation by adding an externally located heat exchanger and fan system to provide circulation of heated air and thus improving stove fuel-use efficiency, such addition of a heat exchanger has several disadvantages. For example, an externally added heat exchanger is unattractive in appearance, requires an unnecessarily large amount of material for its construction, is unduly expensive, and is not very efficient.
External appearance of a stove previously supplying heat only by radiation may be preserved by addition of a heat exchanger within the combustion chamber of the stove, but installation of such a heat exchanger presents problems of accomplishing airtight sealing, which is essential to prevent inclusion of harmful gases from the burning fuel in air circulated within the heated room, and to maintain regulation of the fire in an airtight stove. An additional problem presented by addition of internally located heat exchangers to existing stoves is that their presence within the combustion chamber will upset the designed convection current characteristics of the stove, reducing fuel burning and heating efficiency of the stove. In fact, since less heat output is required in modern well-insulated homes, many modern wood burning stoves are of a small size, compared to old-fashioned heating stoves, and introduction of an internally located heat exchanger would cause severe restriction of the capacity of a small stove.
As was noted, in order to be most effective, a heat exchanger requires provision of a fan or similar device to force circulation of air through a heat exchanger. While the best location for hot air outlets is in the front of such a stove, to provide heated air to the main part of a room having a stove in the customary location in a corner or end of the room, simple open pipes in the front of a stove would be unsightly.
What is needed, therefore, is a stove having a pleasing outward appearance, and including an integral forced air heat exchanger having hot air outlets which are functional yet also have a pleasing appearance.